Write a function f(a, b) which takes two character string arguments and returns a string containing only the characters found in both strings in the order of a. Write a version which is order N-squared and one which is order N.

StringOrder.java

/**
 * Created by harshadura on 2/17/16.
 */
public class StringOrder {
    public static void main(String args[]) {
        String inputA = "harsha";
        String inputB = "sanjeewa";

        System.out.println(orderByNSq(inputA.toCharArray(), inputB.toCharArray()));
        System.out.println(orderByN(inputA.toCharArray(), inputB.toCharArray()));

    }

    public static char[] orderByNSq(char[] a, char[] b) {
        String ret = new String();

        for(int i = 0; i < a.length; i++)
            for(int j=0; j <b.length; j++) {
                if(a[i] == b[j]) {
                    if(ret.indexOf(a[i]) == -1)
                        ret += a[i]; 
                    break; 
                }
            }

        return ret.toCharArray();
    }

    public static char[] orderByN(char[] a, char[] b) {
        String ret = new String();
        int[] flags = new int[256]; 

        for(int i = 0; i < b.length; i++)
            flags[b[i]] = 1;

        for(int j=0; j <a.length; j++)
            if(flags[a[j]] == 1) {
                ret += a[j]; 
                flags[a[j]] = 0;
            }
        return ret.toCharArray();
    }

}